Half-duplex morse carrier system



L. ESPENSCHEED HALF DUPLEX MORSE CARRIER SYSTEM Filed Auz. 11. 192] 3 Sheets-Sheet IIlk LENA-52 L. ESPENSCHIED BALE DUPLEX MORSE CARRIER SYSTEM Filed Aug. 11, "1921 3 Sheets-Sheet 2 avwmtoz $513 ELMO M4013 Oct. 28. R924, 1,533,452

1.. ESPENSCHI EDV I HALF DUPLEX MORSE CARRIER SYSTEM Filed Aug. 11, 1921 3 Sheets-Sheet 5 wumtoz Patented Get. 28, 1924.

, barren srarss LLOYD ESPENSGI-IIED, O1" QUEENS, NEW YORK, ASSIGNOR T O .EL'MERICAN TELEPHONE AITD TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

HALF-DUPLEX MORSE CARRIER SYSTEM.

Application filled August 11, 1921. Serial No. 491,511.

T all whom it may concern: v

Be it known that T, LLOYD EsPnNsoHrnD, residing at Queens, 1n the county of Queens and State of New York, have invented certems, and more particularly to multiplex si 'nalinu s stems em lo in carrier cur- D u D rents for transmission purposes.

One of the purposes of this invention is to produce a simple terminal apparatus for half-duplex Morse operation over carrier channels. In order to simplify the terminal apparatus in accordance with the present invention, it is proposed to use the same vacuum tube as a detector when receiving and as an oscillator when transmitting. A salient feature of the terminal arrangement involves the association of the vacuum tube with the transmission circuit through aubalanced circuit arrangement involving a hybrid coil and two channels, one channel being used for transmitting and the other for receiving. This permits the tube when functioning as a detector to receive oscillations through the receiving channel, and when functioning as an oscillator to transmit oscillations tothe transmission circuit over the transmitting channel;

Other and further features of the invention will be clear'from the following description, when read in connection with the accompanying drawing, the three figures of which illustrate different circuit arrangements embodying the principles of the invention.

Referring to Figure 1, ML designates a main transmission line having associated therewith a transmitting circuit TL and a receiving circuit RL, these circuits being associated with the main line through the usual hybrid coil 1, and being rendered substantially conjugate by means of a balancing circuit MN for simulating the impedance of the main line. The receiving circuit RL includes a plurality of selective circuits F F etc., these selective circuits being adapted to associate the receiving circuit with the vacuum tube device of the terminal apparatus. The vacuum tube and associated circuits connected with but one of the selective devices is illustrated, but it will be understood that similar apparatus will be provided for each. channel. The apparatus associated with the selective device RF, includes a vacuum tube VT of the usual three-element type. A tuned circuit or other selective device RF," is included in the grid circuit of the vacuum tube. This tuned circuit is coupled with the tune-d circuit or selective device RF, and renders the vacuum tube selective of the received carrier frequency when receiving and serves to determine the frequency of the vacuum tube when functioning as an oscillator, as will be described later. The output circuit of the vacuum tube VT includes a receiving relay HR for controlling the circuit of an operating magnet 20 of a loop controlling relay.

RR, sothat a sounder S in the loop L will be actuated in response to detected signals. The relay RR constitutes part of the mechanical repeating apparatus for associating the loop with the vacuum tube circuit, so that signals may be transmitted to and from the loop, as will be described later.

The tuned circuits RF, and RF, .are coupled together through windings .10 and 11 of a transformer, and a third winding 12, arranged in. inductive relation to the windings 10 and 11, is connected to the plate cir cuit. A transmitting relay TR is provided for controlling the circuits of the vacuum tube. This relay is normally energized and when in this condition establishes a connection from the filament of the vacuum tube VT through the windings 12 and 11 in series to the grid of the tube. Under these conditions, the tube functions as a simple detector. WVhen the transmitting relay is deenergized, the connection from the filament of the tube is shifted so that it is extended to the junction point between the windings 11 and 12. The winding 12 is now in the plate circuit and the winding 11 in the rid circuit, so that a feed-back coupling is established to permit the tube to oscillate. An auxiliary battery 13 is included in this con.-

nection in series with the normal. grid battery 14 to change the grid potential to such a value as to render the tube eificient as an oscillator. The plate circuit includes a transformer 15 for associating the output.

circuit of the vacuum tube when functioning as an oscillator with a tuned circuit TF in the transmitting circuit TL, this association being cheated through the transmitting channel TL The transmit-ting channel TL is normally held open 'by means of a relay TR, which is included in circuit with the transmitting relay TR and is normally energized. hen the relay TR is deenergized to change the vacuum tube circuits to the oscillating condition, the relay TR, is also deenergized to complete the connection through the transmitting channel TL This channel is held open under receiving conditions to prevent signals received by the tube from being transmitted back to the main line. The relay TR is also arranged to short circuit the receiving relay RR to prevent it from responding to oscillations.

The transmitting relay TR and its associated relay TR, are controlled by means of a loop transmitting relay TR whose operating magnet 21 is included in the normallv closed loop circuit L. The loop controlling relay RR has its armature arranged to open and close the loop circuit, and these, and the two relays TR and RR together -constitute the mechanical repeating arrangement hereinbefore referred to for associating the loop with the vacuum tube arrange ment. These relays are provided with auxiliary holding magnets 21 and 20, respectively, for preventing false operation of the relays, as will be described later. Each of these magnets is normally short-circuited, the magnet 21 being short-circuited over the contact of the relay RR and the magnet 20 being short-circuited over the contact of the relay TR.

Under normal conditions, the loop L is closed so that the relay TR is energized to maintain the circuits of the transmitting relay TR and the associated relay TR, closed. The transmitting channel TL is, therefore, held open and the circuits of the vacuum tube are maintained in such relation by the relay TR that the tube functions as a simple detector as already described. @scillations incoming over the main line ML are, therefore, transmitted through the tuned circuit RF, to the grid circuit of the tube VT, and the signals detected by the tube actuate the receiving relay RR to open the circuit of the operating magnet 20 of the relay RR,. As the holding magnet 20 of this relay is normally short-circuited, the armature of the relay RR is permitted to fall off, thereby opening the loop circuit and causing the sounder S to respond. This operation deenergizes the operating winding 21 of the relay TR, but since the short-circuit controlled by the contacts of the relay RR is removed from about the holding magnet 21 at the same time that the loop circuit is opened, the armature of the relay TR is prevented from falling ofi to repeat the signals back to the main llne ML.

When it is desired to transmit signals from the loop L to the main line, the key K may be actuated to open the loop, thereby deenergizing the operatin magnet 21"of the relay TR. As the holding magnet 21 is short-circuited, the armature of the relay is permitted to fall off, thereby opening the circuit of the transmitting relay TR and the associated relay TR The deenergization of the relay TR shifts the connections of the vacuum tube from; detecting condition to oscillating condition and short-circuits relay RR. The relay TR, at the same time closes the transmitting channel TL so that the oscillations generated by the vacuum tube VT are transmitted through the transformer 15 over the channel TL through the selecting circuit TF and over the transmitting circuit TL to the main line ML. The armature of the relay TR, in falling off, removes the short-circuit from about the auxiliary magnet 20 of the relay RR and prevents false operation of said relay in case the receiving relay RR should respond to the transmitted signals. Such response is prevented by the short-circuiting of relay RR as previously described.

A slightly modified arrangement of the apparatus is illustrated in Fig. 2. In this case the relay TR is arranged to shift the connection from the filament in the same manner as described in connection with Fig. 1 in order to change the vacuum tube VT from a detector to an oscillator. The transformer 15, for associating the oscillating output circuit of the tube with the transmitting circuit TL over the transmitting channel TL is, in this instance, included in the grid side of the vacuum tube circuit when arranged for detector operation, rather than in the plate side as shown in Fig. 1. No arrangement is provided for opening the transmitting channel TL when the circuit is thus connected, and the inductance of the transformer 15 is permitted to cooperate with the capacity in the transmitting circuit TL to constitute a tuned selecting device. It is unnecessary to open the transmitting channel TL during receiving conditions, for the reason that if the transmitting and receiving circuits TL and RL are properly balanced, the high frequency energy incoming over the main line MEL will divide equally between these two circuits, and the energy transmitted through the selecting circuit TF to the input circuit of the vacuum tube VT will be balanced, so far as its tendency tobe transmitted through the transformer 15 is concerned, by the normal energy transmitted into the channel TL The energy is not balanced as regards the input circuit of the vacuum tube VT, however, and the vacuum tube functions to detect signals from the high frequency energy. Tntransmitting, the transmitting relay TR will be deenergized in a manner previously de- "ill scribed, thereby changing the circuit conditions of the tube so as to render the tube oscillatory. The oscillations thus set up Will be transmitted through the transformer 15 and over the channel TL to the main line The energy thus transmitted to the main line is prevented from reactin 1n the receiving circuit RL by means of t e hybrid coil 1 and the balancing network MN.

Fig. 3 illustrates an arrangement in which the oscillations are set up by the vacuum tube arrangement through the unbalanced condition existing between the transmitting and receiving circuits TL and RL. While normally these circuits are sufliciently well balanced so that the transmission over the circuit TL to the receiving circult RL may be considered negligible, in some instances a considerable degree of unbalance exists and this may be utilized in the generation of oscillations. The vacuum tube apparatus in this instance comprises two tu es, a tube VT which functions as an amplifier and a tube VT, which normally will function as a detector. A receiving relay ER is included in the output circuit of the tube VT, and its grid circuit includes olarizing batteries 25 and 26. The latter attery is arranged to be short-circuited by the contact of the transmitting relay TR when said relay is deenergized. When both batteries are effectively in series in the id circuit, the potential upon the grid wil be such that the tube is eflicient as a detector, but when the transmitting relay'TR is deenergized in transmitting signals, the short-circuitmg of the battery 26 results in such a change of the grid potential that the tube is efiiclentfor amplifying or oscillating. An auxiliary relay TR is associated with the transmitting relay TR for holding open the transmitting channel TL which is coupled wlth the output circuit of the tube VT, through the transformer 15.

Under normal conditions, the transmit-- ting channel TL is held open so that received oscillations from the main line ML pass into the receiving circuit and are selected by means of the tuned circuit RF, and I RF, into the input circuit of the amplifying tube VT,. The oscillations are then amplified and impressed upon the grid circuit of the tube VT, which, by reason of the fact that the battery 26 is short-circuited,

operates as a detector, so that the detected signals actuate the receiving relay RR and are repeated into the loop by means of the repeating apparatus as described in connection with Fig. 1. When signals are transmitted from the loop, the repeating apparatus operates as already described, to deenergize the relays TR and TR,". The

former relay short-circuits the battery 26 to change the potential of the grid of the tube VT so that it will be efiicient as an oscillator. The relay closes the transmit-- ting channel TL Consequdntly, the ener y from the output circuit of the vacuum. tu e VT, is transmitted over the channel TL into the transmitting circuit TL to the line ML. As a portion-of this energy passes into the receiving circuit RL due to the un-' circuit is established, so that the oscillations I generated will pass to the main line ML ivhenever the key K is actuated to open'the It will be obvious that the general rinciples herein disclosed may be emb ied in many other organizations widely difi'erent from those illustrated, without departing from the spirit of the invention as defined inthe following claims. \Vhat is claimed is:

1. In a signaling system, a transmission circuit and carrier apparatus associated therewith, said carrier apparatus including a. transmitting circuit and a receiving circuit substantially conjugate with respect to each other, and a vacuum tube associated with said transmitting circuit and said receiving circuit, said Vacuum tube functioning under certain conditions as a detector, and under other conditions as a generator of oscillations.

2. In a signaling system, a transmission clrcuit and carrier apparatus associated therewith, said carrier apparatus including a transmitting circuit and a receiving circuit substantially conjugate with respect to eachother, a vacuum tube associated with said'transmitting circuit and said-receiving circuit, and connections whereby under certain conditions said vacuum tube functions to detect signals from the carrier currents transmitted from said transmission circuit over said receiving circuit to said vacuum tube, and whereby under other conditions said vacuum tube functions to generate oscillations for transmission over said transmitting circuit to said transmission circuit. a 3. In a signaling system, a transmission circuit and carrier apparatus associated therewith, said carrier apparatus including a transmitting circuit and a receiving circuit substantially conjugate with respect to each other, a translating device associated with said transmitting and receiving circuits, and circuits for said translating device including switching means, said switching means bemg so arranged that under certain conditions the translating device func- ,tions as a detector and under other conditions functions as a generator of oscillations, and a local subscribers loop and mechanical repeating apparatus for interconnecting said local subscribers loop with said translating device, said repeating apparatus including means for repeating signals detected by, said translating device to said loop, said repeating apparatus also including means responsive to signals originating in the loop to'control said switching means to cause said translating device to generate oscillations. I

circuit and carrier apparatus associated therewith, said carrier apparatus including a transmitting circuit and a receiving circuit substantially conjugate with respect to each other, a vacuum tube associated with said transmitting and receiving circuits and circuits for said vacuum tube including switching means, said switching means being so arranged that under certain conditions the vacuum tube functions as a detector and under other conditions functions as a generator of oscillations, and a local subscribers loop and mechanical repeating apparatus for interconnecting said local subscribersloop with said vacuum tube, said repeating apparatus including means for repeating signals detected by said vacuum tube to said loop, said repeating apparatus also including means responsive to signals originating in the loop to control said switching means to cause said vacuum tube to generate oscillations.

5. In a signaling system, a transmission circuit and carrier apparatus associated therewith, said carrier apparatus including a translating device, circuits for said translatin device so arranged that under certain conditions it functions as a, detector and under other conditions it functions as a generator of oscillations, a transmitting circult and a receiving clrcult for interconnectin said translating device to said transmlssion circuit, said transmitting and receiving circuits being substantially con u- 4:. In a signahng system, a transmission gate with respect to each other, a subscribers loop and echanical repeating apparatus for associating said subscribers loop with said translating device, means for normally holding open said transmitting circuit, said repeating apparatus comprisingmeans Whereby when said translating device functions as a detector, the detected signals may be re-- peated to said loop, said repeating appar'a tus also including means responsive to signals originating. in said loop for closing said transmitting circuit and adjusting the circuits of said translating device so that it generates oscillations for transmission over receiving circuit for" interconnecting said vacuum tube to said transmission circuit, said transmitting and receiving circuits being substantially conjugate with respect to each other, a subscribers loop and mechanical repeating apparatus for associating said .subscribers loop with said vacuum tube, means for normally holding open said transmitting circuit, said repeating apparatus comprising means whereby when said vacuum tube functions as a detector, the detect ed signals may be repeated to said loop, said repeating apparatus also including means responsive to signals originating in said loop for closing said transmitting circuit and adjusting the circuits of said vacuum tube so that it generates oscillations for transmission over said transmitting circuit to said transmission circuit.

In testimony whereof, l have signed my name to this specification this 9th day of August, 1921.

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